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Publication numberUS3790407 A
Publication typeGrant
Publication dateFeb 5, 1974
Filing dateDec 28, 1970
Priority dateDec 28, 1970
Also published asDE2148785A1, DE2148785B2, DE2148785C3
Publication numberUS 3790407 A, US 3790407A, US-A-3790407, US3790407 A, US3790407A
InventorsMerten R, Pickart D
Original AssigneeIbm
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Recording media and method of making
US 3790407 A
High coercivity metallic magnetic material in finely divided particle form is milled with a lubricant to convert it to a leafing flake. The flakes thus obtained are mixed with a suitable binder vehicle and solvent and coated on a non-magnetic substrate to form a leafed coating in which most of the magnetic flakes float to the surface of the vehicle to form a relatively continuous thin layer of high coercivity magnetic material. When the binder vehicle is dried or cured it firmly adheres the thin layer of magnetic material to the substrate and also provides adhesion between the flakes of magnetic material to thus provide a wear and corrosion resistant magnetic recording media capable of high resolution recording.
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United States Patent [191 Merten et al.

[ RECORDING MEDIA AND NIETHOD OF MAKING [75] Inventors: Ronald A. Merten; Don E. Pickart,

both of Boulder, C010.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: Dec. 28, 1970 [21] App]. No.: 102,127

[52] US. Cl 117/240, 117/234, 117/235 [51] Int. Cl. H0lf 10/02 [58] Field of Search 117/235, 240, 234, 100 M; 252/6254 [56] References Cited UNITED STATES PATENTS 3,525,694 8/.1970 Bisschops et al. 117/235 3,139,354 6/1964 Wolff 117/235 3,592,687 7/1971 Schnell et al. 117/235 X 2,106,882 2/1938 Betz 117/235 X 3,389,105 6/1968 Bolger 117/l00;100 X 2,954,552 9/1960 Halpen 117/100 X 3,245,826 4/1966 Luce et al.. 117/240 X 3,503,882 3/1970 Fitch 117/240 X 2,418,479 4/1947 Pratt et al. 117/240 X 2,570,856 10/1951 Pratt et al. 117/240 3,015,627 l/l962 Ayers et a1 117/235 X Feb. 5, 1974 3,047,428 7/1962 Goto et a1 117/235 X 3,574,685 4/1971 Haines 117/235 X 1,912,887 6/1933 Chipman 117/239 X OTHER PUBLICATIONS Friedman et al., IBM Tech. Dis. Bu1l., Vol. 9, No. 7, Dec. 1966, p. 779.

[57] ABSTRACT High coercivity metallic magnetic material in finely divided particle form is milled with a lubricant to convert it to a leafing flake. The flakes thus obtained are mixed with a suitable binder vehicle and solvent and coated on a non-magnetic substrate to form a leafed coating in which most of the magnetic flakes float to the surface of the vehicle to form a relatively continuous thin layer of high coercivity magnetic material. When the binder vehicle is dried or cured it firmly adheres the thin layer of magnetic material to the substrate and also provides adhesion between the flakes of magnetic material to thus provide a wear and corrosion resistant magnetic recording media capable of high resolution recording.

5 Claims, No Drawings 1 RECORDING MEDIA AND METHOD OF MAKING BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to methods of making magnetic compositions and coatings for use in the preparation of magnetic recording media.

2. Description of the Prior Art Magnetic compositions for use in preparing magnetic recording media have been prepared in numerous ways. The earliest recording media were in the form of solid magnetic wires which did not utilize coating technology. Subsequently, magnetic recording media took on the form of particulate magnetic material, in the form of magnetic oxide or magnetic metallic particles, dispersed throughout a binder or vehicle, coated on a substrate, and dried or cured while still in a dispersed state. More recently, small quantities of magnetic recording media have been prepared using various plating technologies to form thin, continuous films of magnetic metallic material on a substrate. Each of these types of media has both its advantages and its shortcomings.

Solid metallic magnetic wire provides a very efficient use of material and a high remanent moment; however, the wire has a tendency to twist or rotate in use and thus is subject to signal loss and distortion. Magnetic media formed from particulate magnetic particles dispersed in a binder and coated on a two-dimensional substrate avoids the twisting problem inherent in wire. However, particulate-binder media suffers in that it is capable in most instances of achieving relatively low coercivities, low remanent magnetization, and, due to limitations in coating technology, is subject to production as a relatively thick coating, on the order of 50 to 500 microinches thick. Coatings of this thickness are of limited utility for the recordation of high-resolution, high-density signals, such as those required in modernday processing systems. The thickness of the media causes the broadening of magnetic signals, and thereby limits the density and resolution obtainable from thick coatings of particulate magnetic material in a binder. Additionally, particulate-binder media requires uniform dispersion of the magnetic particles throughout the binder and is subject to the existence of discontinuities of magnetic material from place-to-place in the coating. As the density of recording increases, the likelihood of a to-be-recorded signal coinciding with a magnetic discontinuity increases. When this occurs, there will be a complete loss of signal in the media and a concomitant loss of the data represented by that signal.

Various plated media have obviated some of the shortcomings of particulate media. Plated media may be provided by electroplating, electroless plating, vacuum plating, gas plating, thermal decomposition, sputtering, or other means, and is usually in the form of continuous thin films on a two-dimensional substrate. The continuity of such films avoids signal loss inherent in particulate media. The thinness of the film, normally on the order of about 500 to 5000 angstroms (between about 1 and microinches), allows for high-density, high-resolution recording without the pulse broadening experienced in thicker films. However, inherent in the thin metallic nature of such coatings is their greatest shortcoming. By their very thinness, such films are subject to wear and damage from ordinary handling and use, so that their life is severely limited. Additionally, the thin metallic films are subject to deleterious oxidation and corrosion which further limits their material properties and usefulness.

Therefore, the problem of the prior art is to provide a magnetic recording media which is in the form of a thin coating having the high coercivity and remanent moment necessary for high resolution recording and which exhibits the physical characteristics of wear and corrosion resistance. As is detailed herein, such a media is provided by utilizing leafing techniques in the production of magnetic recording media.

The use of leafing metallic pigments in the production of paints and decorative coatings is a wellestablished art. The development of this portion of the paint industry very closely parallels in time the development of particulate magnetic recording media. Primarily, leafing techniques have been limited to the production of coatings including leafed aluminum, although leafed bronze, zinc, gold, silver, and other lustrous metallic leafing flakes have been incorporated in coatings. It is noted that the literature teaches that leafed flakes are generally a minimum of about 25 to 44 microns in diameter (corresponding to 500 mesh and 325 mesh). On a number of occasions, magnetic material in both flaked and non-flaked forms, has been included in leafing coatings to provide a physical function. In several instances, the inclusion of magnetic material in leafing paints has been coupled with the use of an external magnet to provide a substance within the wet paint which could be influenced by an external magnetic field to adjust the reflective character of the paint. In other instances, leafing magnetic material has been utilized in a coating to provide a layer for absorbing microwaves.

Despite the long parallel history of bright leafing paints and magnetic record media, and the close relationship of both of these technologies to the paint industry, there is no known instance of the application of leafing metal technology to the formation of magnetic recording media. The present invention is believed to bridge this technological gap for the first time and provides means for forming magnetic recording media utilizing a unique form of leafing technology.

SUMMARY OF THE INVENTION The present invention provides compositions and methods for producing magnetic recording media by leafing techniques. In the practice of the present invention, finely divided metallic magnetic material, 5 microns or less in diameter, is milled with a lubricant to render them plate-like and both hydrophobic and oleophobic. The plate-like magnetic particles or flakes are then dispersed in or on a binder vehicle, including volatile solvents and coated upon a substrate. This results in the leafing of the magnetic flakes at the surface of the binder vehicle to form a thin, relatively continuous metallic magnetic layer upon the vehicle. Subsequently, the binder vehicle is cured or dried to provide an adherent layer between the substrate and the leafed magnetic flakes and also to provide for adhesion from flake-to-flake.

The resulting media may be in the form of a disk, tape, drum, loop, cylinder, stripe, strip, card, or other form. However, it is provided with a thin relatively continuous film of high coercivity magnetic metallic material firmly adhered to a substrate, which film is resistant to both abrasive wear and corrosion, due to the interaction between the flakes and the vehicle binder, and which is capable of recording high-density, highresolution magnetic signals.

The foregoing objects, features, and advantages of the invention will be apparent from the following description of the preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Any malleable metallic magnetic particle having high coercivity may be used in the process of the present invention. The magnetic flake materials should have coercivities greater than about 250 oersteds so as not to be subject to demagnetizing effects. As used herein, the term metallic is intended to encompass not only the pure magnetic metals or non-metals, but also alloys of magnetic metals with other metals. The only requirement in this respect is that the materials be malleable and therefore subject to milling to a flake-like shape within the size range of about 0.01 to 5 microns, possess coercivity greater than 250 oersteds after milling, and be subject to leafing.

Suitable magnetic materials include certain forms of finely divided, highly magnetic iron and steel, produced, for example, by vaporization or carbonyl techniques, as well as materials produced by electrodeposition upon liquid cathodes, or from suitable baths to provide finely divided particles. Other techniques for producing finely divided magnetic materials for leafing include controlled chemical decomposition of chemical plating baths, other forms of chemical oxidation and reduction, and other techniques. Mixtures of high coercivity finally divided metallic magnetic materials are also contemplated as being within the scope of the present invention. As noted hereinabove, the initial source of magnetic material is limited only in that it must be available in finely divided form, it must be malleable, and it must retain high coercivity after being milled to a flake.

In the practice of the present invention, the magnetic metallic powders are mixed with a suitable solvent, such as mineral spirits, and a lubricant, such as stearic acid, and then milled, for example, in a steel ball mill. In the mill, the friction and hammering action of the balls reduces the powder to minute, flat, flake-like particles. During milling, the lubricant is readily absorbed by thenewly formed surfaces of the magnetic particles and prevents the magnetic flakes from being welded together. When milling has proceeded to the desired point, the process is stopped and the mill sludge screened by a fine mesh sieve to eliminate larger particles and agglomerates. The final thickness and size of the flakes is a function of the amount of magnetic particles charged into the mill and the milling time.

The slurry which passes the fine mesh sieve has excess solvent removed by filtration,-with the particles forming a filter cake containing about 80 percent to 90 percent, by weight, magnetic flakes, the balance being absorbed lubricant and retained solvent. At this point, if dry magnetic powder flakes are desired, the remaining solvents in the filter cake may be removed under vacuum conditions. Finally, the filter cake is normally thinned with clean mineral spirits or other solvent to a paste containing 60 to percent magnetic flakes, by weight.

When this paste of leafing magnetic flakes is mixed with a suitable leafing binder vehicle and solvent, the

flakes will float to the surface of the vehicle and orient themselves parallel with the surface to produce a bright, level, relatively continuous, thin magnetic film. The flakes in the leafing layers are normally on the order of about 0.001 to about 1.0 micron thick, while the flake diameter is in the range of about 0.01 to 5 microns. Flake diameters of about 0.1 to about 1 micron and flake thicknesses of 0.01 to 0.2 micron are preferred. Flakes having a diameter greater than about 5 microns cannot be tolerated as they tend to lose the desired magnetic characteristics, and limit signal density and resolution. The magnetic flakes are arranged in layers of from about 5 to 15 particles deep, with a thin coating of vehicle between each flake and layer. Due to the formation of this multiple overlapping layer structure and the coating on each flake, the continuity of magnetic materials in the coating is exceptionally high. The film is thin and exhibits physical strength and durability, while the flakes are protected from corrosion and wear. The thickness of the flake coating ranges from about 0.005 to 3 microns thick.

The leafing characteristics exhibited by these coatings is the result of the magnetic flakes rising to the vehicles surface and remaining there. The flake particles rise because of convection currents existing in the binder vehicle due to solvent evaporation. The speed of travel of the magnetic flakes through the binder vehicle depends upon the vehicles chemical make-up, the character of the solvent, and the viscosity of the system. High speed flake travel is encouraged by a low viscosity system which exhibits high surface tension, high density, and a high rate of solvent evaporation. Modification of these vehicle and solvent characteristics will have a direct effect upon the speed of migration of the magnetic flakes within the binder vehicle. The leafing tendency of the flakes is also the greatest where these magnetic particles exhibit minimum thickness and maximum area.

The propensity of the magnetic flakes to stay at the surface of the vehicle is due to the interfacial tension between the flake surface and the binder vehicle. At the vehicles surface, each magnetic flake makes a finite contact angle with the binder vehicle due to the absorbed lubricant film on the flake. Additionally, the vertical component of the surface tension of the vehicle acting along the line of contact between the magnetic flake and the binder vehicle, and the upward hydrostatic head of the vehicle, which is a function of the binder vehicle density, serves to cause the flake to remain at the surface of the vehicle.

The binder vehicle chosen must not only serve to give the requisite mechanical strength and adhesion to the leafed magnetic articles when dry and cured, but also must be compatible with the lubricant utilized in producing the leafed particles. For example, where stearic acid is the lubricant of choice, it primarily comprises a soft absorbed film at the surface of the platelet, although some evidence of chemical reaction exists. The destruction of this film can be caused quite easily by either mechanical or chemical means. Extended contact with strong acids, moisture, polar solvents, lead compounds, as well as strong agitation, and aeration can effectively destroy this film. Unsaturated fatty acids and short-chained fatty acids are also detrimental to the leafing quality of the flakes. Therefore, a binder vehicle must be chosen which avoids these destructive forces and which can be mixed with the flakes with a minimum of grinding, moisture, and air.

Binder vehicles of choice will have a high surface tension and include solvents which also exhibit high surface tensions. As a choice of solvent, any of a large number of oils can be employed, specifically, a large variety of hydrocarbon solvents. The selection of a suitable solvent of this type does not involve critical requirements, but rather a choice among many known liquid solvents, to suit such factors as toxicity, cost, and convenience in the preparation of the specific coating composition. Among the large variety of known and suitable solvents are high-grade volatile mineral spirits, aromatic petroleum solvents, straight aromatic solvents, or high-flash solvent naptha. Specific examples of these solvents include xylol, turpentine, and benzol. Other hydrocarbon solvents that can be employed are toluene, xylene, petroleum aliphatic naptha, and petroleum aromatic naptha. In some cases, the solvent may be or include polar solvents if their contact with the flakes is minimized.

Dispersion of the magnetic flakes or paste in the vehicle is accomplished by simple mixing. Preferably, the vehicle is added to the magnetic flakes. The desired amount of each component is determined prior to mixing, measured, and mixed with steady gentle stirring, avoiding excessive agitation.

Among vehicles suitable for use in the practice of the present invention are phenolic resins, silicone resins, alkyd resins, the various latex emulsions, resins, polyester resins, polyurethane resins, and epoxies. Other typical, but not limiting, vehicles for use singularly, or in combination for preparing various recording media are cellulose esters and ethers, vinyl chloride, vinyl acetate, acrylate and styrene polymers and copolymers, polyamides, aromatic polycarbonates, and polyphenol ethers.

Suitable lubricants for use in the practice of the present invention include alkyl and alkenyl fatty acids having from 14 to 22 carbon atoms in the alkyl or alkenyl chain. Specific examples are stearic acid, or its equivalent, which is most commonly used, and also other fatty acids, such as oleic, lauric, myristic, behenic, palmitic, and ricinoleic. The materials used in the practice of this invention may be pure, or they may be of commerical quality. For example, commercially available stearic acid also contains small amounts of palmitic and oleic acids intermixed as a constituent thereof. Not only can mixtures of the fatty acids be utilized in the practice of this invention, but also derivatives of the fatty acids, such as the metal soaps, can be used with facility. Other useful lubricants include petroleum lubricants, such as ordinary lubricating oils and greases, or hydrogenated vegetable oils. Fluorocarbon resins are also suitable for use as lubricants in the practice of the present invention. Conveniently, the total quantity of lubricants in the flake paste produced by the milling operation may be in the range of about 1 percent to about percent, by weight, of the magnetic flakes present.

While ball milling has been indicated as being the most common mode of practice of this invention, it is to be understood that that is only one conventional method of preparing leafing magnetic flakes and that there are other procedures, such as the use of hammer stampers, dry stampers, and attritors which give equivalent results. Time of milling can range from several hours to several days depending upon the method chosen, the amount of charge in the mill, and the speed at which the mill is run. It is not uncommon to include projections known as lifters within the ball mill along its walls to provide means to lift the balls, and thus allow them to cascade or cataract onto the balls below with the greatest impact.

Once prepared, the flake-binder vehicle dispersion may be applied to a suitable substrate by roller coating, gravure coating, knife coating, or spraying, or by other known methods. The terms dry and cure as applied to the binder vehicle are each intended to encompass the drying or curing process which is suitable for providing a stable binder coating.

In preparing recording media, the magnetic flakes usually compromise about 25-90 percent, by weight, of the solids in the mixture applied to the substrate; although, shortly after coating, leafing takes place so that from about 50 percent to 90 percent of the flakes rise to the surface of the binder vehicle. The substrate upon which the mixture is coated is often a flexible resin, such as polyester or cellulose acetate material; although, other flexible materials, as well as rigid base materials, are more suitable for some uses. The specific choice of non-magnetic substrate, vehicle, solvents, or method of application of the magnetic composition to the support will vary with the properties desired and the specific form of magnetic recording media being produced. Although not describedin detail, other ingredients and additives may be added to the mixture as stabilizers, contact lubricants, or for other purposes.

The following examples are illustrative of the present invention:

EXAMPLE I Magnetic cobalt-phosphorous was prepared from a solution similar to those used in the preparation of plated material by chemical reduction. The solution contained cobalt ions and hypophosphite reducing agent, citrate complexing agent, and ammonium hydroxide to control the pH of the solution. Decomposition of the bath with the resulting formation of fine powdered magnetic material was induced by raising the temperature of the solution near its boiling point and by adding small quantities of palladious chloride to the solution. The resulting particles had an average size of about 0.1 micron, a density of 7.9 grams per cc, and an intrinsic coercivity of about 825 oersteds as measured on a vibrating sample magnetometer at 4,000 oersteds.

A sample of this cobalt-phosphorous weighing 650 grams was placed into a 1.3 gallon steel ball mill fitted with lifters and loaded with 15 pounds of inch stainless-steel balls. 20 grams of stearic acid powder and 350 grams of mineral spirits were also introduced into the ball mill. The mill was rotated at a speed of 103 revolutions per minute, which was sufficient to produce cataracting of the steel balls and result in a maximum impacting condition between the balls in the mill. Milling under these conditions was carried out for 48 hours, and the wet slurry of cobalt-phosphorous flakes was removed from the mill, washed with fresh mineral spirits, and filtered to form a cake of approximately percent pigment, by weight. To this cake was then added slowly, with gentle mixing to provide smooth dispersion, a freshly prepared 50 percent solution of equal parts of Mondur CB-75, castor oil, and toluene solvent. Mondur CB-75 as supplied by Mobay Chemical Company is a trifunctional isocyanate prepolymer of toluene diisocyanate and trimethylol propane. The cobaltphosphorous flakes constituted about 70 percent, by weight, of the solids in this mixture. The resulting coating was applied to a flexible l.5 mil thick biaxially oriented polyethylene terphthlate film by conventional knife coating techniques to a wet thickness of about 1000 micro-inches.

Immediately after application, the cobaltphosphorous flakes were noted to rise to the surface of the binder vehicle in the form of what appeared to be a substantially continuous reflective metallic film. After drying and curing were completed, the binder vehicle was found to be in the form of a flexible crosslinked polyurethane. The coating was inspected by electron micrograph and found to have a total thickness of 200 microinches, with approximately 90 percent of the cobalt-phosphorous particles at the surface in a layer having a thickness in the range of about 0.5 to 0.8 micron. When slit to form magnetic recording media, the media was found to have an intrinsic coercivity of 719 oersteds and a squareness ratio of 0.34. It was capable of passing a recording head repeatedly without visible wear and recorded data at a rate of 1600 flux changes per inch with excellent results.

As previously noted, the surface of the media had the appearance of a substantially continuous reflective metallic film; however, when examined under an optical microscope, it was found to consist of discrete particles, each particle apparently in its own thin polymer or lubricant package. When subjected to temperature and humidity conditions of 85 C and 85 percent RH. for 24 hours, the media showed no signs of detrimental oxidation or corrosion.

EXAMPLE II Using the same source of cobalt-phosphorous particles as in Example I, magnetic flakes were prepared as in Example I, and the flakes mixed with a 50 percent solution of Epon i001 and Versamid 115. Epon 1001, as supplied by Shell Chemical Company, is an epoxy terminated reaction product of bisphenol A and epichlorohydrin. Versamid 115, as supplied by General Mills, is a polyamide. This mixture was coated on a smooth brass disk with a standard spraying technique to a wet thickness of approximately 1.5 mil. Immediately after coating, the metallic cobalt-phosphorous flakes were noted to appear at the surface of the vehicle binder.

As in Example I, after the vehicle was dried and cured to form a crosslinked epoxy, the media so produced exhibited excellent recording characteristics, good wear and corrosion resistance, and was fully useful as a high-resolution recording media. An ultramicrotomed cross section of the media indicated the coating had a final dry thickness of about 300 microinches, with the metallic film having a thickness of about 0.3 to 0.6 micron. The magnetic film appeared to contain approximately 80 percent of the cobaltphosphorous flakes.

Other media were prepared utilizing other high coermetallic magnetic particles were converted to flakes as taught herein, using both stearic acid and other lubricants during the milling process. The resulting flakes were dispersed in various binder vehicles and coated on several different types of substrates. In some instances, the binder was coated on the substrate first followed by a coating of flaked magnetic particles in a solvent. All produced excellent high resolution recording media exhibiting good wear and corrosion resistance.

EXAMPLE Ill The techniques of the present invention were applied to several low coercivity magnetic materials to determine their ability to produce high resolution recording media. Samples of nickel having a coercivity less than 200 oersteds, iron powder having a coercivity less than oersteds, permalloy iron-nickel having a coercivity of less than 50 oersteds and steel having a coercivity less than 10 oersteds were obtained from various sources, comminuted to a size less than 5 microns by ordinary milling techniques, and then milled utilizing lubricants and solvents as in Example I. The resulting flakes were formed into a dispersion with castor oil and Mondur CB-75, coated on substrates and dried, as in Example I. Each of the resulting media was fully reflective and magnetic; but when tested for high resolution recording, they were found to be entirely inadequate due to demagnetization effects.

Other modifications of and variations in the procedure and resulting pigment and coating material will also be apparent to those skilled in the art without departing from the spirit of this invention. While preferred procedures and materials have been described with considerable particularity, the invention is not restricted thereto, but illustrations given are to be taken as representative of the scope and character of the invention with the recognition that equivalent procedures and materials may be used. Certain features of the invention may be used without other features, and changes may be made as respects details of procedure and material without departing from the spirit of this invention. Reference is therefore to be had to the appended claims for a definition of the invention.

What is claimed is:

1. The method of making magnetic recording media consisting essentially of the steps of:

subjecting finely divided, metallic magnetic particles having coercivities greater than about 250 oersteds to mechanical milling in the presence of a leafing lubricant and a volatile solvent to produce flakes having diameters in the range of about 0.01 to 5 microns, thickness in the range of about 0.001 to 0.2 micron, coercivities greater than 250 oersteds, and having on their surfaces a leafing lubricant film;

mixing said flakes with a non-magnetic binder vehicle and a volatile solvent, said binder being of different composition than said leafing lubricant;

coating the mixture onto-"a non-magnetic substrate;

allowing the metallic magnetic flakes to leaf to the surface of the coating mixture; and then drying said coating mixture.

2. Magnetic recording media consisting essentially of:

a non-magnetic substrate;

a non-magnetic binder vehicle adherently coated upon said substrate; and

. 3 ,7 90,407 9 10 a relatively continuous layer of metallic magnetic 3. The magnetic recording media of claim 2 wherein Particles, Said layer of PaftiCleS being about 0005 the magnetic particles are about 0.01 to 1 micron in dito 3 microns thick and having a coercivity greater ameter and about 01 to 2 micron thick than 250 oefsteds Said lalfer of metallic magnetic 4. The magnetic recording media of claim 2 wherein pamcles bemg Supported m and upon sald binder 5 the magnetic particles are cobalt-phosphorous pro- F wlth Said bmdgr vehlcle s.ervmg i duced by chemical reduction from an aqueous cobalt particles together, said magnetic particles being bath formed of flakes, said flakes being about 0.01 to 5 5. The magnetic recording media of dam 2 wherein microns in diameter, about 0.001 to 1 micron in thickness, and having on their surfaces a l fi the binder vehicle is selected from the group consistlng bricant film, said leafing lubricant being of differof polyurethane and epoxy polymers. ent composition than said non-magnetic binder.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1912887 *Dec 18, 1929Jun 6, 1933Andrew Le Roy ChipmanMethod of making records for reproducing sounds
US2106882 *Dec 12, 1936Feb 1, 1938Magnaflux CorpPaste of paramagnetic particles for use in the examination of paramagnetic materials for flaws by the magnetic method
US2418479 *Feb 16, 1944Apr 8, 1947Du PontProcess for orienting ferromagnetic flakes in paint films
US2570856 *Mar 25, 1947Oct 9, 1951Du PontProcess for obtaining pigmented films
US2954552 *Feb 1, 1946Sep 27, 1960Otto HalpernReflecting surface and microwave absorptive layer
US3015627 *Jul 6, 1960Jan 2, 1962C K Williams & CoGamma ferric oxide for magnetic impulse record members
US3047428 *Jan 26, 1959Jul 31, 1962Fuji Photo Film Co LtdMagnetic recording material
US3139354 *Mar 31, 1961Jun 30, 1964Rca CorpMagnetic recording element containing magnetic particles treated with werner-type complex compound and method of manufacture thereof
US3245826 *Jun 12, 1963Apr 12, 1966Clevite CorpMagnetic recording medium and method of manufacture
US3389105 *Mar 5, 1965Jun 18, 1968Alcan Metal Powders IncFlake metal powders coated with fluorocarbon resin
US3503882 *Sep 6, 1966Mar 31, 1970Turco Paint & Varnish CoPaint composition
US3525694 *Aug 30, 1967Aug 25, 1970Agfa Gevaert NvMagnetic recording material
US3574685 *Jan 14, 1969Apr 13, 1971IbmManufacture of magnetic particles by reacting iron,cobalt,or nickel salts with oxalic acid salts in dialkyl sulfoxide
US3592687 *Jan 6, 1969Jul 13, 1971Basf AgProduction of magnetic recording media
Non-Patent Citations
1 *Friedman et al., IBM Tech. Dis. Bull., Vol. 9, No. 7, Dec. 1966, p. 779.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4087582 *Nov 4, 1974May 2, 1978Fuji Photo Film Co., Ltd.Magnetic recording medium
US4097620 *May 2, 1977Jun 27, 1978Xerox CorporationMagnetic toner particle coating process
US4171274 *Jul 7, 1977Oct 16, 1979Xerox CorporationAlteration of tesselated magnetic particles by fracture
US4192902 *May 2, 1977Mar 11, 1980Xerox CorporationIn situ coating then spray drying of magnetic toner
US4246316 *Mar 17, 1978Jan 20, 1981Fuji Photo Film Co., Ltd.Magnetic recording medium
US4247407 *Apr 23, 1979Jan 27, 1981Victor Company Of Japan, LimitedMagnetic recording composition
US4290808 *Mar 23, 1979Sep 22, 1981Allied Chemical CorporationMetallic glass powders from glassy alloys
US4332863 *Aug 5, 1980Jun 1, 1982Tdk Electronics Co., Ltd.Magnetic recording medium
US4465737 *Jan 31, 1983Aug 14, 1984Fuji Photo Film Co., Ltd.Magnetic recording medium
US4473619 *Jan 24, 1983Sep 25, 1984Porco Daniel AMagnetic audio recording tape and method of preparation thereof
US4533565 *May 24, 1984Aug 6, 1985Fuji Photo Film Co., Ltd.Method for surface treatment of ferromagnetic fine powder and forming a magnetic recording device
US4590127 *Jan 22, 1985May 20, 1986Sumitomo Chemical Company, LimitedAbrasive used in magnetic recording medium and production thereof
US4687705 *May 8, 1985Aug 18, 1987Fuji Photo Film Co., Ltd.Magnetic recording medium
US4992329 *Mar 24, 1989Feb 12, 1991Kabushikikaisha Riken & Simizu Construction Co.Magnetic-shielding sheet
US5164263 *Dec 21, 1989Nov 17, 1992E. I. Du Pont De Nemours & Co.Aluminum nitride flakes and spheres
US5280401 *Nov 25, 1991Jan 18, 1994Hitachi, Ltd.Magnetic recording medium, method for producing same and magnetic recording apparatus
US5869148 *Feb 9, 1993Feb 9, 1999Webcraft Technologies Inc.Process for the in-line, high speed manufacturing of magnetic products
US6251475 *Apr 30, 1999Jun 26, 2001Agfa-GevaertPreparation of a magnetic layer
US6902807 *Sep 13, 2002Jun 7, 2005Flex Products, Inc.Alignable diffractive pigment flakes
US7047883Mar 11, 2003May 23, 2006Jds Uniphase CorporationMethod and apparatus for orienting magnetic flakes
US7241489Jan 20, 2004Jul 10, 2007Jds Uniphase CorporationOpaque flake for covert security applications
US7258900 *Nov 13, 2002Aug 21, 2007Jds Uniphase CorporationMagnetic planarization of pigment flakes
US7258915Aug 14, 2003Aug 21, 2007Jds Uniphase CorporationFlake for covert security applications
US7300695Jan 4, 2005Nov 27, 2007Jds Uniphase CorporationAlignable diffractive pigment flakes
US7517578Dec 22, 2004Apr 14, 2009Jds Uniphase CorporationMethod and apparatus for orienting magnetic flakes
US7550197Jul 11, 2007Jun 23, 2009Jds Uniphase CorporationNon-toxic flakes for authentication of pharmaceutical articles
US7604855Oct 20, 2009Jds Uniphase CorporationKinematic images formed by orienting alignable flakes
US7625632Aug 2, 2006Dec 1, 2009Jds Uniphase CorporationAlignable diffractive pigment flakes and method and apparatus for alignment and images formed therefrom
US7645510Oct 4, 2005Jan 12, 2010Jds Uniphase CorporationProvision of frames or borders around opaque flakes for covert security applications
US7667895Feb 23, 2010Jds Uniphase CorporationPatterned structures with optically variable effects
US7674501May 1, 2006Mar 9, 2010Jds Uniphase CorporationTwo-step method of coating an article for security printing by application of electric or magnetic field
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US7880943Oct 1, 2007Feb 1, 2011Jds Uniphase CorporationPatterned optical structures with enhanced security feature
US7934451May 3, 2011Jds Uniphase CorporationApparatus for orienting magnetic flakes
US7938901 *Mar 31, 2004May 10, 2011Silberline LimitedMetal pigment composition
US8025952Sep 27, 2011Jds Uniphase CorporationPrinted magnetic ink overt security image
US8118963Jun 27, 2007Feb 21, 2012Alberto ArgoitiaStamping a coating of cured field aligned special effect flakes and image formed thereby
US8343615Apr 4, 2006Jan 1, 2013Jds Uniphase CorporationDynamic appearance-changing optical devices (DACOD) printed in a shaped magnetic field including printable fresnel structures
US8658280Oct 28, 2011Feb 25, 2014Jds Uniphase CorporationTaggent flakes for covert security applications having a selected shape
US8726806Sep 26, 2012May 20, 2014Jds Uniphase CorporationApparatus for orienting magnetic flakes
US8999616Jan 9, 2014Apr 7, 2015Jds Uniphase CorporationTaggent flakes for covert security applications having a selected shape
US9027479Oct 6, 2009May 12, 2015Jds Uniphase CorporationMethod and apparatus for orienting magnetic flakes
US9102195Jan 9, 2013Aug 11, 2015Jds Uniphase CorporationArticle with curved patterns formed of aligned pigment flakes
US9164575Oct 31, 2007Oct 20, 2015Jds Uniphase CorporationProvision of frames or borders around pigment flakes for covert security applications
US9257059Nov 29, 2012Feb 9, 2016Viavi Solutions Inc.Dynamic appearance-changing optical devices (DACOD) printed in a shaped magnetic field including printable fresnel structures
US20040051297 *Mar 11, 2003Mar 18, 2004Flex Products, Inc., A Jds Uniphase CompanyMethod and apparatus for orienting magnetic flakes
US20040151827 *Jan 20, 2004Aug 5, 2004Flex Products, Inc., A Jds Uniphase CompanyOpaque flake for covert security applications
US20050009846 *Dec 18, 2003Jan 13, 2005Fischer Peter Martin2,6,9-Substituted purine derivatives and their use in the treatment of proliferative disorders
US20050037192 *Aug 14, 2003Feb 17, 2005Flex Prodcuts, Inc., A Jds Uniphase CompanyFlake for covert security applications
US20050106367 *Dec 22, 2004May 19, 2005Jds Uniphase CorporationMethod and apparatus for orienting magnetic flakes
US20060077496 *Nov 15, 2005Apr 13, 2006Jds Uniphase CorporationPatterned structures with optically variable effects
US20060097515 *Dec 20, 2005May 11, 2006Jds Uniphase CorporationKinematic images formed by orienting alignable flakes
US20060194040 *May 1, 2006Aug 31, 2006Jds Uniphase CorporationTwo-step method of coating an article for security printing
US20060198998 *Apr 4, 2006Sep 7, 2006Jds Uniphase CorporationDynamic appearance-changing optical devices (dacod) printed in a shaped magnetic field including printable fresnel structures
US20060263539 *Aug 2, 2006Nov 23, 2006Jds Uniphase CorporationAlignable Diffractive Pigment Flakes And Method And Apparatus For Alignment And Images Formed Therefrom
US20070051272 *Mar 31, 2004Mar 8, 2007Wheeler Ian RMetal pigment composition
US20070139744 *Dec 12, 2006Jun 21, 2007Jds Uniphase CorporationSecurity Device With Metameric Features Using Diffractive Pigment Flakes
US20070172261 *Jan 15, 2007Jul 26, 2007Jds Uniphase CorporationApparatus For Orienting Magnetic Flakes
US20070183047 *Apr 17, 2007Aug 9, 2007Jds Uniphase CorporationOptically Variable Security Devices
US20070195392 *Apr 23, 2007Aug 23, 2007Jds Uniphase CorporationAdhesive Chromagram And Method Of Forming Thereof
US20080003413 *Jun 27, 2007Jan 3, 2008Jds Uniphase CorporationStamping A Coating Of Cured Field Aligned Special Effect Flakes And Image Formed Thereby
US20080019924 *Jul 11, 2007Jan 24, 2008Jds Uniphase CorporationNon-Toxic Flakes For Authentication Of Pharmaceutical Articles
US20080024847 *Oct 1, 2007Jan 31, 2008Jds Uniphase CorporationPatterned Optical Structures With Enhanced Security Feature
US20080096009 *Jun 7, 2005Apr 24, 2008University Of DelawareHigh Frequency Soft Magnetic Materials With Laminated Submicron Magnetic Layers And The Methods To Make Them
US20080107856 *Oct 31, 2007May 8, 2008Jds Uniphase CorporationProvision of Frames Or Borders Around Pigment Flakes For Covert Security Applications
US20080171144 *Oct 30, 2007Jul 17, 2008Jds Uniphase CorporationPrinted Magnetic Ink Overt Security Image
US20100002275 *Jan 7, 2010Jds Uniphase CorporationSecurity Device With Metameric Features Using Diffractive Pigment Flakes
US20100208351 *Mar 18, 2010Aug 19, 2010Nofi Michael RSelective and oriented assembly of platelet materials and functional additives
USRE45762Sep 26, 2013Oct 20, 2015Jds Uniphase CorporationPrinted magnetic ink overt security image
DE3030360A1 *Aug 11, 1980Mar 26, 1981Tdk Electronics Co LtdMagnetisches aufzeichnungsmedium
EP0027255A1 *Oct 8, 1980Apr 22, 1981Hitachi Maxell Ltd.Magnetic recording medium
U.S. Classification428/148, 428/532, 428/842.3, G9B/5.275, 428/336, 360/134, 252/62.54, G9B/5.277, 428/480, G9B/5.281, 427/130, 428/328
International ClassificationG11B5/71, G11B5/725, G11B5/714, G11B5/72, G11B5/70, H01F1/06, H01F1/032
Cooperative ClassificationH01F1/06, G11B5/71, G11B5/714, G11B5/725
European ClassificationH01F1/06, G11B5/725, G11B5/71, G11B5/714